I think a consistent challenge in transfeminist analysis is the question of where trans women fit into the classical man-woman scheme of patriarchy. You have some transfeminists asserting that trans women are exactly identical to cis women, and others asserting that trans women actually represent a sort of "third sex." Conversations go back and forth about this and my current thoughts are that there are compelling arguments on either side, but that they're both deeply flawed and limited because of their typically one-sided, metaphysical analysis.
Looking at the material evidence, it is plainly apparent that trans women are women proper - we are forced into the same spheres of labor as other women within our classes. Most of us are trapped in low-wage (often highly feminized) work, or are forced out of the formal legal economy and into sex work, long-term unemployment and begging just to afford food, and so on. As with cis women, a small number of us (mostly limited to the imperial core) are professionals who can access higher education, well-paying jobs, and so on. We can see plainly that, when all other factors are equal, trans women make markedly less money through employment than do cis women, cis men, and also trans men, which is consistent with and easily explained by our real existence as a type of specially-exploited woman, the same way a Black woman will typically make less than a white woman, a periphery woman less than an imperial core woman, and so on. We are just another kind of woman with an added layer of special exploitation, and one which is not incompatible with any other such layer.
On the other hand, we can look at the way we are spoken of and commonly regarded in normal social life. It seems plainly apparent that many people, maybe even most people, do indeed regard us as a third sex even if they would not use that term. Cis women, for the most part, do not get they/themmed incessantly the same way we do when someone is aware of our trans status. We're totally unwelcome in sexed spaces (bathrooms, changing rooms, etc), on a bio-physical level we are regarded as alien or as if we function completely differently from a cis woman or a cis man (despite HRT making us bio-physically extremely similar to cis women, and extremely different from cis men. The vast majority of trans women are either on HRT or desire to be on it). Even bourgeois trans women, take for instance the US politician Sarah McBride, are regarded with so much distaste and hatred by other bourgeois women. A phenomenon I've observed repeatedly in my own life is that when in public, strangers will consistently and exclusively address me as female, as a woman, with she/her, up until I have to share my ID (as part of getting a job, to access medical care, to buy alcohol, etc) - I have been unable to get the sex marker on my ID changed, and as soon as a stranger notices that, it's immediately apparent that I instantly become something "other" to them, something unknown and foreign and scary, and they don't really know what to do about it and usually refer to me very minimally or with they/them for the remaining duration of the interaction. There are countless other such phenomena we can raise to provide evidence for the fact that we seem to be regarded as a third sex, but I'll end there.
What's happening here? On a material level, trans women are simply women proper, but on an ideological level, trans women seem to be widely understood as a third sex. Much to the distaste of those attempting to carry out a metaphysical analysis, this is a contradictory state of affairs - the reality as it exists within the financial statistics and within the medical journals and in a visit with a client is distinct from the reality that exists within people's heads, in the realm of the ideal. We can attempt to pick one side or the other and say that it is the truth of transfeminine existence, but I see this as a mistake. Rather, I think it is much more coherent to regard the true nature of transfeminine existence as this contradiction, as the class of people who are truly women on every material level but who are also widely regarded as something separate from and foreign to womanhood even at the same time as those same people regarding us as such produce the conditions that create our special-exploitation as just another underclass of women.
For the most part, this is not done with conscious intent, but rather, it's the natural cross product of the general conditions of capitalism and class society, the current ideological and material formation of patriarchy, and the specific neuroses non-transmisogynized people hold about trans women in the context of these greater systems.
The same way the proletariat is defined by its contradiction with the bourgeoisie rather than as something with independent existence, our nature as trans women is defined by contradiction to both men and cis women on a material level but also on an ideological level the very concept of a "cis" woman - the idea that women are not a socially constructed category but are instead something natural, immutable, in possession of existence separate from class society and patriarchy in particular. Or, to put it another way, trans women are defined as the class of women violating the perfect Platonic forms of patriarchy as people imagine them.
This is mostly just a collection of thoughts, or you could think of it as a set of notes I've made public for the sake of seeing how well they resonate with other Marxist trans women. Someday I might write something longer and more formal about this, but this has been on my mind for the last few years and this is the general conclusion I've reached.
There may well be more than 2 genders, but from the point of view of the patriarchy, there is only one gender and you either have enough of it or you lack it to varying degrees. It is all about being male enough in the right kind of ways. Everyone else is some kind of despicable, exploitable, or a mix of both.
